Starting and ballasting apparatus for electric discharge devices



NOV. 16, 1943. SHORT 2,334,587

STARTING AND BALLASTING APPARATUS FOR ELECTRIC DISCHARGE DEVICES Filed Jan. 28, 1942 Invent or: ThomasT. Short,

b WW6.

His Abb orney.

Patented Nov. 16, 194 3 STARTING AND BALLASTIN G APPARATUS FOR ELECTRIC DISCHARGFQDEVICES Thomas T. Short, Fort Wayne, Ind., assignor to General Electric Co New York mpany, a corporation of Application January 28, 1942, Serial No. 428,564

Claims. ('01. 315-282) My invention relates to apparatus for starting,

and ballasting electric discharge devices employed on alternating current circuits. Although my invention is applicable to the starting and control-' ling of discharge devices of various forms, it has,

been particularly devised to be used with fluorescent lamps now cominginto extensiveuse. Such lamps comprise a transparent tubular envelope containing mercury vapor at low pressure and having the inner surface of its side walls coated with a suitable phosphor which under the influence of an electric discharge through the mercury. vapor produces fluorescence. The lamp electrodes v which are mounted in the ends of the envelope.

are filamentary in form and are 'coated with a suitable electronemitting material. Such a lamp requires for its starting the application of a voltage impulse considerably higher than the voltage necessary to. keep the lamp in operation after it has been started. In as much as the voltage required to start such a lamp is materially less if the lamp electrodes are heated prior to the application of the starting voltage and since less injury is done to the lamp if its electrodes are preheated it has become common practice to heat the electrodes to the point of electron omission prior to the application of the starting voltage. It is also common practice to effect such preheating of the electrodes and to produce the necessary voltage across the lamp to cause it to break down byv using a starting device connected across the lamp'in series with the lamp electrodes which device-opens the circuit after the electrodes are suitably heated.

To avoid the delay incident to the preheating of the electrodes, to avoid the cost of starting devices and to avoid the cost of the additional! wiring necessitated by the installation of the starting devices, instant starting of such lamps has been effected by applying thereto a voltage sufficient to make them break down immediately even with cold electrodes. For that purpose transformers with the accompanying drawing and its'scope will be pointed out inthe appended claims. I

Referring to the drawing, Fig, 1 is a circuit I diagram illustrating one form of my invention;

Fig. 2 is a diagram showing the voltage and flux curves obtained with my invention and Fig. 3

i is a circuit diagram illustrating a'modification.

In Fig. 1, the electric discharge device I, represented as a fluorescent lamp, having electrodes 1 and 2, is shown connected to be supplied through the switch 3 from the source 4 of alternating current; such for example as a 115volt, 60 cycle lighting circuit. For providing the necessary high voltageto cause thedevice l to start" without preheating its electrodes and for providing operating ballast for the device after it has been started, I have devised the reactor-trans-' former 5 which will nowjbe described. As shown in Fig. 1, it comprises a corestructure built up of a series of channel shaped laminations 6 and bar laminations l, the laminations 6 in adjacent 4 layers being reversely arranged so as to break the joints with the bar laminations in the well under I stood manner. The core thus formed has the two legs 8 and'9. Intermediate said legs is a'stack of bar laminations forming the magnetic shunt Hi, the ends of the laminations forming the shunt being separated from the adjacent portions of have been used having high leakage but such transformers have the disadvantage that as a result of their use the power factor of the energy drawn from the source of supply is objectionably low, for example 20 to 25%.

It is the object of my invention to provide improved apparatus by which the necessary high voltage may be obtained for starting an electric discharge device without preheating its electrodes and without producing an objectionably low power factor.

My invention will be better understood from the following description taken in connection the core by the non-magneticgapsl I. The gaps are very small, hence the. coupling between the primary and the secondary I5 is so small during the normal running of the device that it may be neglected and the secondary considered as a series ballast. At that time the primary will draw only a small exciting current determined bythe gaps Surrounding the leg 8 is'the winding l3 which. in the form shown, has the intermediate tap [4 which connects with one side oi the source 4 through the switch 3, the lower end of, the-windsource 4. .Thus that part of the winding below the tap is the primary and the entire Winding is a secondary. The upper end of the winding l3 connects with the electrode 1! of the device I through the secondary winding IS on the leg 9, the other electrode 2' being connected directly with the source 4 as shown. In the event that the source of supply 4has a voltage high enough to operate the device I without being stepped up or, conversely, if the'device l is 'adapted to operate on the voltage of the source,-the tap It may be omitted and the switch 3 may connect directly with the upper end of the winding [3. Those portions of the laminations 6 forming the leg 9 each have the narrow transverse. opening I! punched therein which openings are" so arranged that when the plates are'stacked in themanner described, the openings ll will aline with each The resulting opening through. the leg 9 justed to provide the correct value of current to be takenby the device.

Referring now to Fig. 2, the voltage'wave applied to the device I upon theclosure of the control switch 3" is represented by the curve I9 which from the zero point 20. to-approximately' the point 2| and. from approximately the point 22 to the following zero point "represents the voltage applied to the device by the winding it. During these intervals the portions iii of the leg 9v are saturated. Atapproxirnately the point 21 the portions I81 begin to desaturate whereby the flux through the leg. 9 undergoes; a. rapid rate of" change as''- shown: by the flux curve 25 untilapproximately the time thatjthepoint 22":

is reached whenthose portions I! again saturate.

As a result of this rapid rate of change'of flux as it passes 'throughzero, there is induced in the winding 15. and. superposedl upon the voltage wave obtainedf from-ithe winding l3, the voltage peak shown'at' zl which" peak i's-sumcient. to cause the device I to: break: down.. After the device has started, energy will be :drawn'fromthe source at approximately the powerfactor of the device being reduced only :bythe-smail. exciting current in the primary Withapparatus such as I have stacking'the F-shapedilaminations' 30 and thebar laminations 31 together with the rectangular laminations 32 separated from the adjacent ends of the first mentioned laminations by the nonmagnetic gaps 33 whereby, the'laminations 32 form the magnetic. shunt; This form of my invention difiers only in the relative arrangement of the magneticshunt. with respect to the legs ing by including'a capacitor in circuit with the device. Thus in themodification illustrated by Fig. 3'1 have-shown" the capacitor 34 in series with the device, the capacitance thereof'being suflicient to produce a leading current in the device;

What Lelaim as newand' desire to secure by Letters Patent of the United States, is:

l. Incombination, a source of alternating current supply, an electric discharge device arranged to be energized therefrom, and means connected between said source" and said device for superposing a peak on'the voltage wave of said source, said means comprising a transformer having a core providing for high magnetic leakage and having a secondary connected in series between said source and said device, that part of said core whose flux is limited to that interlinking said secondary having a portion constructed to saturate.

2. In combination, a source of alternating current supply, a transformer having a core providing for high leakage and having its primary connected to be energized from said source, and

an electric discharge device connected to be supplied from said source through a secondary of said transformer, that part of said core whose flux is limited to that interlinking said secondary having a bridged air gap at which saturation occurs.

3. In combination, a source of alternating current supply, an electric discharge device, a transformer having a primary arranged to be energized from said source, and a secondary, and having a core providing a leakage flux path and a flux path interlinking said secondary, said latter flux path including a bridged air-gap, and

meansconnecting said device and said secondary in serieswith said source whereby a peak is superposed on the voltage wave supplied to said device from said source and energy is drawn from the source at a higher power factor.

4. In combination, an electric discharge device, a core structure providing a closed magnetic path, primary and secondary windings interlinking said path at different parts thereof, said structure including a part providing a flux leakage path shunting said secondary winding and having that part of said path interlinked with said secondary winding providing an air gap and a saturating portion in parallel therewith and means connecting said device and said secondary winding in series across said primary.

5. In combination, an electric discharge device, a core structure having a plurality of spaced legs, a primary winding on one of said legs, a secondary winding on another of said legs, and another of said legs forming a magnetic shunt, said leg having thereon the secondary winding being provided with a bridged air-gap and means connecting said device and said secondary winding in series across said primary.

6. In combination, an electric discharge device, acore structure comprising spaced members and other spaced members connecting them, a primary winding surrounding one of said connecting members, a secondary winding surrounding another of said connecting members, and another member arranged between said first mentioned members and separated therefrom by an air-gap at each end thereof, said member surrounded by the secondary winding being provided with a bridged air-gap and means connecting said device and said secondary Winding in series across said primary.

'7. In combination, an electric discharge device, a core structure having a plurality of windings interlinking a magnetic circuit provided thereby, said structure including a part providing a leal age path between said windings and a part having an air gap and a saturating portion in parallel therewith, and means connecting said device and one of said windings in series across the other of said windings.

S. In combination, an electric discharge device,

' a transformer having a primary arranged to be supplied'by a source of alternating current, a secondary, and a core, said core being constructed latter flux path including a bridged air gap, and

means connecting said device, said secondary, and the other part of said two-part winding in series across said one part.

'10. In combination, an electric dischargedevice, an electromagnetic structure including a. winding connected in series with said device and a source of current supply for ballasting the device after it has started and including means energized from said source for inducing in said winding a peaking voltage during a part of each half cycle for starting the device.

THOMAS T. SHQRT. 

